Are there authorities to whom it would be worth reporting this event?
Any other recommended actions?
Is it valuable to anyone for me to post other examples? (They are pretty much variations on the above.)

No. Assuming you're in the US, attacking a site like that is probably against some law, but the only organizations with the jurisdiction and resources to actually do something about it have far more important things to do with their resources (unless your site happens to be for a major financial or governmental organization).

Any other recommended actions?

If the site is already secured then no.

Is it valuable to anyone for me to post other examples? (They are pretty much variations on the above.)